The present invention relates to a process for preparing 4-oxo-4,5,6,7-tetrahydrobenzofuran derivatives. More specifically, the present invention relates to a process for preparing 4-oxo-4,5,6,7-tetrahydrobenzofuran derivatives of the formula (I): ##STR1## wherein R and R.sup.1 are hydrogen atom or an alkyl group.
The benzofuran derivatives of the formula (I) are useful as an intermediate for synthesis of drugs, particularly as an intermediate for synthesis of 4-hydroxyindole which is a key intermediate for synthesis of Pindolol, or as an intermediate for synthesis of various kinds of 4-substituted indole drugs (K. Saemeli: Helv. Physiol. Acta, 25, 221(1967); Japanese Patent Unexamined Publication No. 103160/1981).
As a process for preparing 4-oxo-4,5,6,7-tetrahydrobenzofuran derivatives, there hitherto has been known Feist-Benary synthesis. That is, a process in which 1,3-cyclohexanedione is condensed with chloroacetoaldehyde in the presence of a base (E. Bisagni et al.: Bull. Soc. Chim. Fr., 4041(1971)). The abovementioned method, however, is not suitable for the industrial production because of low yield of the desired 4-oxo-4,5,6,7-tetrahydrobenzofuran derivative, as is utmost about 40%.
It is an object of the present invention to provide a process for preparing 4-oxo-4,5,6,7-tetrahydrobenzofuran derivatives.
Another object of the present invention is to provide a process in which 4-oxo-4,5,6,7-tetrahydrobenzofuran derivatives can be easily prepared in a high yield by condensing a 1,3-cyclohexanedione derivative with chloroacetoaldehyde.